MATLAB: How to pass a variable between a m-file and another m-file that runs a gui

guiguidem-filem-file guimatlab gui

Hello,

I'm trying to pass a variable between one m-file and another m-file that initiates gui.

More specifically:

I have one m-file (mfile1) that is concerned with the initiation of gui, however, some calculations are made in other m-file(mfile2).

I would like to pass some variables in the mfile2 to the mfile1.

Is it possible?

Thank you in advance.

Best Answer

M files can contain scripts or functions but variables can only be passed to functions so the m-file must be written as a function [see Scripts vs Functions and Create Function in Files].

For example,

mfile2

function [output] = mfile2(input) 
    % add 1 to the input and pass the result to mfile2.
    y = input + 1; 
    
    % Send y to mfile1 and get the result
    % mfile1 divides y by 2 to z equals (input+1)/2
    z = mfile1(y);
   
end

mfile1

function [output] = mfile1(input)
    % divide the input by two
    output = input/2;
end

All variables needed in a function must either be passed into the function as inputs or defined within the function. If your functions interact with your GUI, pass the handle structure into the function.

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Delete the associated .m file and reopen the GUI in GUIDE. In GUIDE, open Tools > GUI options... check "Generate FIG file and MATLAB file" and save the GUI.

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You should review the documentation on how to write a function, since your above code is not a correctly written function. First, come up with a name for your function, e.g. myFunction. Then create a new file called myFunction.m somewhere on the MATLAB path (e.g. your working directory). Then in that file put your code. E.g.,

function result = myFunction(V)
result = V;  % <-- allocate the result variable, copying all elements
%

% Insert your code here to create the result variable from the V variable
%
return
end

I will give you some hints about correcting your code:

Change this loop:

for i=1:1:6;  % <-- hard coded for exactly 6 elements

to this

for i=1:numel(V)  % <-- allows any size input

The following test has an error in the logic (compare this carefully with the requirement):

if [V(i)<0 | mod(V(i),2)==0 | mod(V(i),4)==0]

The following line has an error on the right hand side calculation (compare this carefully with the requirement):

    V(i)=i*i;

If you don't see what the errors are, step through a small example by hand and compare that to the code result. E.g., at the command line type this:

V=[10,4,7,-8,-3,-12];
myFunction(V)

Best Answer

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